DICTYOPHYTON. 131 



probable that this framework was held together by a delicate spicular membrane, 

 for crushed examples occur in which portions of the framework are frequently 

 displaced without having the symmetrical arrangement destroyed ; but in some 

 instances the spicules are broken up and mingled together, in the same manner as 

 in certain specimens of Protospongia. 



This form was originally regarded by Conrad as a subgenus of Orthoceras ; it was 

 afterwards referred by Hall to marine Algae. Still later Prof. Schimper expressed 

 doubts of its being a plant, and stated that the structure much nearer resembled the 

 skeleton of siliceous sponges. Prof. Ferd. Rcemer rightly compared the structure 

 with that of Tetragonis Danbt/i, M'Coy, with which it is undoubtedly congeneric. 

 After this Mr. R. P. Whitfield *, without being aware of Schimper's and Rcemer's 

 comparisons of the genus to sponges and allied forms, or at all events without 

 mentioning the fact, refers Dictyophyton and some other genera to sponges like the 

 recent Euplectella. 



Hall enumerates eight other species of Bictyojjhyton, based on differences of outer 

 form ; it is probable that they may be all included in the present species. The 

 Tetragonis Eifeliensis, Rcemer, very closely resembles the present form, and there 

 can be hardly a doubt of its belonging to the same genus. 



Distribution. Chemung Group, Upper Devonian : Cohocton, Steuben County, 

 Western New York. 



DiCTTOPHTTON Danbti, M'Coy, sp. 



1855. Tetragonis Danhyi, M'Coy, Brit. Pal. Foss. p. 62, pi. 1 D. f. 7 & 8. 

 1880. Tetragonis Danbyi, Ferd. Eoemer, Leth. Geogn. 1 Th. p. 304. 



Sponge subcorneal or subovate, imperfect both at the basal end and at the summit. 

 Length about 25 mm. The surface is divided into larger and smaller squares by 

 apparently continuous lines, in the same manner as in the preceding species, but the 

 sides of the larger squares are not more than 1'5 to 2 mm. in length, thus very much 

 smaller than in B. tuberosum. 



Both M'Coy and Rcemer have referred this form to the genus Tetragonis, Eichwald ; 

 but the typical species of this genus, T. Murchisonii, Eichw. f, though presenting a 

 superficial resemblance to the present form, possesses a structure of a quite different 

 character. From an examination of undoubted forms of Tetragonis from the Silurian 

 of Gotland, I believe that it is a sponge, and that it is very closely allied to Ischa- 

 dites, Murch. 



IMctyophyton Danbyi differs from D. tuberosum, Conrad, and D. Eifeliensis, Rcemer, 

 in its smaller size and the slighter character of the spicular framework. The 

 only specimen which I have seen is M'Coy's figured type in the Woodwardian 



* American Journal of Science, vol. xxii. p. 53. 

 t Urwelt Kusslands, Heft 2, p. 81, t. 3. f. 18. 



s2 



